The present invention relates to a conveying device and to a conveying method for transporting strip portions for cutting with a cutting device from a material strip in transverse direction of the material strip, which strip portions are then laid rooftile wise onto a stacker.
In the manufacture of for instance corrugated cardboard this strip-form material is fed at speeds up to 350 metres per minute to a cutting device in order to divide the material strip transversely into material portions of a desired length. The cutting device comprises two co-acting rollers provided with a knife blade and rotating in opposing directions, between which the material strip for cutting is guided. The knife blades cut the material strip with a scissor action, that is, from one side toward the other. In order during this cutting process to obtain a cutting line at right angles to the transporting direction the knife blades form an angle with the material strip. The cut strip portion is then transported at a higher speed to realize a mutual spacing, whereby it becomes possible to allow the trailing cut edge of the strip portion to fall to a level below the conveying surface during the subsequent stacking overlapping in the manner of roof-tiles. In this way the following strip portion can rise with its leading cut edge against the sloping surface of the stacked strip portion and, optionally using additional brush-like braking means, be slowed down to a conveying speed lower than the supply speed. A spacing of 10-30 cm, depending on the length of the product, is sufficient at a suitable speed to lay the successive strip portions overlapping in the manner of roof-tiles.
A drawback with this known conveying device and conveying method is that during cutting of the strip portion a tensile force is exerted thereon such that after being cut off the strip portion can immediately be accelerated to the desired higher conveying speed. The exertion of this tensile force on the strip portion for cutting off results, however, on the one hand to a greater tolerance for the cut-off length of the strip portion and on the other hand, owing to the relatively slow cutting process transversely of the strip portion, in the cut off portion being pulled crooked, which portion is then laid crooked on the subsequent transporting mechanism. This then leads during stacking in the stacker to damaging of the front protruding corner of the leading cut edge against the stop plate of the stacker, and to crooked stacking.
It is known that attempts have been made to correct the crooked roof-tile-like stacking of the strip portions by using rotating, cone-shaped rollers, between which the crooked strip portions are aligned. If, however, the material strip which is cut by the cutting device consists of a number of material strip bands of equal width, these bands will mutually overlap (so-called interlocking) under the influence of the conical rollers, whereby in the interlocked portion a greater stacking height is created in the stacking station, which can cause the strip portions to prematurely slide off one another to the side.